Variable rheostat



Nov. 1, 1932. R. B. PLANCHE 1,885,373

VARIABLE RHEOS'IAT Filed June 16, 1931 5 Sheets-Sheet 1 Nov. 1, 1932. R.a. PLANCHE 1,335,373

VARIABLE RHEOSTAT Filed Jun e 16, 1951 5 Sheets-Sheet 2 23 221819 "T 16jg wz Nov. 1, 1932. R. B. PLANCHE VARIABLE RHEOSTAT Filed June 16. 19315 Sheets-Sheet I5 Nov. l, 1932. R. B. PLANCHE" VARIABLE RHEOSTAT FiledJ%e 16. 1951 5 Sheets-Sheet 4 1932- R. B. PLANCHE VARIABLE RHEOSTAT IFiled June 16. 1931 5 Sheets-Sheet 5 Patented Nov. 1, 1932 UNITED STATESPATENT OFFICE VARIABLE RHEOSTAT Application filed June 16, 1931, SerialNo. 544,872, and in France June 25, 1930.

while the liquid under the influence of the electric motor being startedis automatically displaced to cover the said stationary electrodes to agreater or less extent in order to vary the resistance and finally causeit to be short circuited.

The invention is embodied in apparatus in which the displacement of theliquid inslde the casing surrounding the electrodes is obtained by apump driven by the electric motor to be started, and which casing isprovided at its upper part with channels for the return of liquid, andalso embodies a flexible diaphragm for closing the channels and which onbeing raised causes through suitable mechanism the short circuiting ofthe electrodes which are connected to the motor.

The invention also includes other devices of particular interest asfollows A stop valve for cutting off the supply of the liquid when thechamber is full and on the other hand to facilitate emptying.

marily when the rheostat is hot and to allow entrance of air when thevacuum becomes too great or vice versa the filling orifice of the casingis provided with an hydraulic valve.

2. To maintain the level of liquid in the casing uniformly constant afilling means from an auxiliary reservoir is provided arranged in theupper part of the apparatus and connnunicating with a tube prolongingthe rheostat at the lower level of the liquid, through a spring valveoperated by the filling valve of the auxiliary reservoir so that it isonly open when this filling valve is completely closed.

3. In order to avoid the use of a packing gland at the outlet from thecasing of the shaft of the lifting pump this outlet of the shaft isarranged prolonged above the upper level of the liquid either by meansof a belt and pulley or gear drive or by arranging the turbinehorizontally so that its shaft will be vertical.

4. To provide the first resistance on starting in cases where the levelof the liquid is insufiicient and to rapidly warm this liquid to raiseit as quickly as possible to its normal temperature and resistantquality for working, the lower ends of the electrodes are connectedtogether by a wire or other electric resistance submerged in the liquid.

The invention will be fully understood on reference to the followingdescription and the accompanying diagrammatic drawings which descriptionand drawings are it mustbe understood only given by way of example.

In the drawings Fig. 1 is a section elevation on line 11 Figs. 2. and 3.I

Fig. 2 is a second sectional elevation at 90 to that shown in Fig. 1 online 22 Figs. 1 and 3.

Fig. 3 is a sectional plan of the terminals and their short circuitingplan on line 33 Figs. 1 and 2.

Fig. 4 is a sectional elevation of a modification on line 4-4 Fig. 5.

Fig. 5 is a further section of the same modification on line 5-5 Fig. 6.

Fig. 6 is a View from above of the rheostat shown in Fig. 5, with thecover removed.

Fig. 7 shows in longitudinal elevation the arrangement of the hydraulicvalve and the automatic filling.

Fig. 8 is a detail sectional view of the rheostat shown in Fig. 4. andembodying a construction permitting omission of the pressure packing fon the shaft of the turbine 8.

Fig. 9 shows diagrammatically the electrodes connected together at theirlower ends by electrical resistances.

Fig. 10 is partly an elevation and partly a section of a modified formof the rheostat in which an auxiliary motor directly actuates theturbine.

Fig. 11 is a plan showing the rheostat connected to the motor controlledthereby.

Fig. 12 is a sectional view of a modified form of the invention.

,According to the invention the apparatus comprises a casing 1 having aplurality of compartments into which is allowed to flow through inlets 2and 3 a predetermined quantity of conducting liquid to bring the levelto a predetermined height. The liquid may be for example a solution ofcrystals of carbonate of soda or common salt dissolved in water.

Three metal plates 4:, 5, 6 electrically insulated from each other aremounted rigidly in the upper compartment 7 of the .casingl from whichthey are also insulated.

At one side of the base of the casing 1 provided a rotor having blades 8enclosed in a casing 9. This rotor is keyed on to a shaft 10 and isrotated by a pulley 11 in one end thereof.

A packing gland 12 prevents the passage of liquid along the shaft. c

The three/plates 4, 5, 6 are provided with terminals 13 by which theyare connected to the terminals of the motor to be started.

At the opposite side these same three plate are connected at 14 to threeother terminals 15, 16, 17, arranged in the cover 18 of the casing butelectrically insulated therefrom.

These last three terminals are provided below the cover with shoulders19, 20, 21 and at the intersection of the lines joining their centres ametal plate 22 is mounted on a flexible insulating diaphragm 23 forminga fluid tight oint between the compartments 7 and 24: inside the cover18.

This metal plate is held against the flexible diaphragm by a smallspring 25.

Immediately under this diaphragm 23.,

(shown on the left hand side of Fig. 2) is.

a passage 26 which places the compartment 7 in communication with thelower reservoir 27 having an outlet plug 28.

The operation of the invention is as follows Suppose .it is desired .tostart an electric motor.

For this purpose the aforesaid rheostat is mounted beside the electricmotor and the shaft of said motor has mounted upon it a small pulleywhich drives, through a belt, the pulley 11 of the aforesaid startingresistance.

The terminals of the motor are connected with the terminals 13 of therheostat.

A predetermined quantity of liquid is run through the plugs 2 or 3 untilthe ends of the electrodes 1, 5, 6 are partially submerged in the liquid(see Fig. 1)

If the circuit through the motor to be started isnow closed this lattercommences to rotate slowly owing to the large resistance offered by theelectrodes 4, 5, 6 which only dip a small distance into the liquid.

In rotating the motor rotates the pulley 11 and the rotor 8 through theshaft 10.

The liquid contained in the compartment 27 is raised by the centrifugalforce developed by the rotor, due to its rotation, and the level of theliquid in the compartment 27 falls, while on the other hand it rises inthe compartment 7 thus progressively immersing the resistanceelectrodes.

Due to this raising of the liquid the resistance is reduced and themotor speed increases until the liquid almost reaches the top of thecompartment 7 and the compartment 27 is nearly empty. i

The resistance of the electrodes has then become very small, partlybecause they are almost completely submerged and partly because they arenearer to each other due to their submersion which reduces the relativeresistance between them.

Theapparatus continuing to rotate causes the liquid to rise but at thismoment it comes in Contact with the flexible diaphragm 23 whichobstructs its passage.

The liquid therefore commences to overflow through the passage 26.

However this passage, although large enough for the escape of air, isnot large enougi to allow the escape of all the liquid lifted by thepump 8 and hence the pressure 'of the liquid on the diaphragm rises andpresses the ring22 upwardly into contact with the shoulders, 1.9, 20, 21which thus short circuit the starting circuit of the motor.

At this moment the liquid circulation is continuing, a part escapesalong the passage 26 and a further part is stopped in the pump itselfdue to the resistance which it meets.

A state of equilibrium is thus reached which maintained until the motoris running normally.

If an accidental breaking of the circuit is now supposed to occur, dueto the opening of a switch or an electric contactor, for example, themotor stops and in proportion diminishes the speed of the rotor 8.

The centrifugal force due to the pump becomes insufiicient and theliquid contained in the chamber 7 escapes back to the reservoir throughthe periphery 29 of the pump.

Under the influence of the upper spring the short circuit is immediatelybroken, since the liquid level falls in the chamber 7, the resistance,increases again until the lower level-of the liquid is reestablished(the position shown in the drawings).

The apparatus is then ready for restarting.

In the modification shown in Figs. 4 6 the casing comprises twosuperposed sections 41 and a connected together at their centre. Thepump 8 is placed in a trapezoidal shaped chamber carrying the lowersection 41. This casing is also provided with holding down lugs 43.

The casing-of the pump is formed with holes the areas of which arecarefully calculated.

The casing Z) on the left hand side of the pump 8 is provided with aregulating screw 0 which takes up the end play of the shaft, while thecasing on the right hand side is formed in one with the end cap 6closing the opening provided in the main casing for the insertion of thepump.

This same cap is provided with a small packing gland f necessary topreventloss of liquid.

The axis of the blades a of the pump is arranged in the centre of themain casing to give an even feed to the upper chamber.

The apparatus is provided with a control valve to prevent a too rapidrising of the liquid level. It comprises a member held against thebottom of the casing with a thick rubber joint 9. This member alsocarries a series of rectangular partitions which may be closed by arubber sheet h.

A perforated bafile e is arranged below to prevent the rubber h frombeing deformed. This baffle also holds the rubber in place.

The operation of this controlling valve is as follows As soon as thepump 8 is started in operation the flow of liquid closes the rubbervalve h and blocks the partitions 7c of the control valve entirelypreventing the passage of water therethrough.

If on the other hand the pump stops and if the level of the liquid hasrisen in the upper chamber the pressure of the water opens this controlvalve and the water rapidly flows into the lower compartment through thelarge openings provided for this purpose.

Means for regulating the rise of liquid is provided for thisarrangement.

It comprises a port Z, formed in the side wall of the pump casing. Thisport is controlled by a plug on which may be screwed more or less intothe port Z.

A second plug a is provided to prevent loss of liquid during operation.

This arrangement of control may further be directly operated fromoutside the casing by replacing the second plug by a rod with a packinggland Fig. 12.

According to whether the rheostat is to be regulated once for all oraccording to need one or other of these arrangements will be adopted.

The filling valve Fig. 5 on the left hand side of the casing is providedwith a filter 0 to prevent any foreign matter which might foul theapparatus from entering.

The plug p forms at the same time an indicator of the liquid level. Itis provided for the purpose with a vertical rod (1 on which are markedthe minimum and maximum levels. In order to be easily removable the plugis formed with a bayonet joint so that in order to ascertain the levelit is only necessary to place the plug in position and remove it againwithout any screwing which mightvary the reading.

The electrodes 4, 5, 6 are formed triangular towards the bottom andrectangular towards the top as shown in Fig. 4 when viewed from the sideand trapezoidal towards the base and rectangular towards the top whenviewed from the front, see Fig. 5.

The combination of these shapes gives the following advantages.

1st. A large electrical resistance when the electrodes are only slightlyimmersed due to small area immersed and their relatively great distanceapart.

2nd. Very small electrical resistance when they are completely immersedimmediately before short cir .uit due to the fact of their large contactsurface and their small distance apart.

They are further spaced equally apart and taken in section the distancewhich separates the two external electrodes from the lateral fl has ofthe upper compartment is half the distance which separates them fromeach other so that their electrical resistance remains constant.

That is to say if 4, 5, 6 are the electrodes above referred to thedistance between 6 and e is identical with that between 4: and 5 andthat etween 5 and 6, the electrical circuit being closed through thecasing from which the electrodes are only separated by twice th halfdistance between each other, that is by the same distance.

At their upper ends these electrodes carry two metallic conducting studsy, welded, screwed or riveted thereto which act as the terminals.

The short circuiting arrangement comprises a diaphragm of rubber orsimilar elastic material, leather or the like. This joint is held inplace by insulation 9" screwed into the cover.

The rubber diaphragm also forms a fluid tight joint.

Inside this insulation 1" a large port is provided which is closed by ametal plate 8 of parallel piped in shape towards its base and thenrectangular, on which is screwed a leather disc t of the shape shown inFig. 5.

he plate 8 is provided with two studs in and 4) which slide in aninsulation member to carried inside the cover.

Copper conductors a0 connect the two rods y affixed to the electrodes.

The insulation 10 is shaped to serve at the same time to insulate thecopper conductors a: connecting the electrodes together.

The operation of the short circuiting arrangement is as follows lVhenthe liquid reaches the upper level the pressure raises the elasticdiaphragm 23 which raises in its turn the metal plate 8 the upper partof which comes in contact with the three copper conductors connectedrespectively to the three electrodes to short ciri seen that ifevaporation occurs and'the rheocuit them.

The bent shape of the copper conductors ences of level there may be.Further the sliding of the studs 24 and '0 in the insulation preventsthis from tipping sideways and therefore keeps it horizontal.

- The casing is provided with cover plate 36 having a control knob 37which may for example be similar to the plug employed for the fillingvalve. This cover plate is formed with three apertures 38 of any desiredshape for the passage of the conducting leads 39.

In the modification shown in Fig. 7 the filling valve in the casing isformed with a tube A dipping into the liquid when this latter afterhaving been raised by the pump is in the upper chamber of the rheostat.This tube further dips into a small reservoir B which remains constantlyfull of liquid even when the rheostat is working that is to say when thelevel is falling (Fig. 1).

This arrangement prevents the evaporation of the liquid when therheostat is hot, that is to say when it has been working for some timeor when the surrounding temperature is very high.

This hydraulic valve also permits the apparatus to breathe, that is tosay to allow air to enter when the vacuum becomes too great orconversely to allow it to escape when the pressure exceeds apredetermined limit.

In order to condense as far as possible the vapour produced, the upperpart of the tube A is mounted in a hollow cylinder C forming acondenser. The space C is maintained at a lower temperature than that ofthe rheostat since it is at about the surrounding temperatureywhile therheostat must be at a higher temperature than the surroundingtemperature due to the transformation of the electrical energy intoheat.This cylinder is formed at its upper end with vents D to permit theescape or entry of ir to the rheostat. A filling arrangement is providedto provide for keeping the level of theliquid in the rheostat absolutelyconstant.

This arrangement consists in forming the cover E as a reservoir forliquid.

At one side the cover is formed with a filling plug F which when it isscrewed down causes a rod G to open a. small valve H allowing liquid toflow from the bottom of the reservoir forming the cover. I

This cover being in place it flows through a tube K which extends intothe rheostat to the lower level of the liquid that is to say to thelevel taken by the liquid in the lower chamber when the pump hasentirely filled the upper chamber. A oint J prevents leakage of theliquid.

If the upper reservoir in the cover is kept .fluid tight, that is tosay, if the filling plug :gives a good contact whatever small differ Fhas been screwed down to prevent escape of liquid from the reservoir, itwill be readily stat loses water, air rising up the tube K allows theliquid inthe reservoir to flow in sufficient quantity to re-establishthe level exactly as in the case of known drinking troughs particularlyused for birds. I

The function of the valve H provided in the base of the cover formingthe reservoir is to prevent during filling of the reservoir E, that isto say when the plug F has been withdrawn, water from this reservoirbeing able to escape into the rheostat and so altering the level. Thiswill not occur when the plug F is replaced and the fiuid tightness ofthe reservoir is reattained and the valve H is opened again and thewater can recommence to how until stable conditions are again set Thesmall quantity which escapes in this way has no appreciable eii'ect onthe operation of the rheostat.

Further to allow for the discarding of a packing gland f as describedabove the pump shaft may be driven by a belt passing over a pulley Marranged as shown in Fig. 8, in an auxiliary casing Nto enable the shaft0 to pass through the casing above the maximum liquid level and so avoidany leakage.

As shown in Fig. 9 the electrodes 4, 5, 6 may be connected together attheir lower ends by a resistance wire such as R R .3 all three arrangedin the same horizontal plane and immersed in the liquid in order.

1. To serve first as a starting resistance if the liquid level is low.

2. To rapidly heat the liquid in contact with this resistance to bringit as quickly possible to its normal temperature and resistant quality.

Lastly as shown in Fig. 10 the drive of the small pump 8 may be carriedout by a small auxiliary motor l? receiving current either from thestator of the motor to be started or from the rotor.

It is preferable to employ in this class of rheostat a non-congelableelectrolite and one only having a small variation in intrinsic powers ofresistance during the raising of its temperature to normal. Anelectrolite which may be advantageously formed by a heat insulatingliquid such as glycerine to which more or less water has been added orother liquid held in suspension or dissolved a conducting powder such asgraphite or suitable mineral salts.

As will be understood and as a result of what has preceded the presentinvention is not limited either to the examples given above or to theirdifferent parts but includes on thecontrary all modifications and moreespecially n as the casing at a point above the level of the upperliquid the plane of rotation being horizontal and the shaft vertical.

What ll claim as my invention and desire to prot ct by Letters Patentis 1. An automatic rheostat for starting electric motors comprising thecombination with stationary resistance electrodes of a casing containingconducting liquid compartments within the casing within one of which theelectrodes are mounted a pump driven by the motor to be start-ed housedwithin a second compartment to pump liquid into the electrodecompartment to progressively immerse the electrodes to a greater extentand means for finally short circuiting the resistance electrodes.

2. An automatic rheostat for starting electric motors comprising thecombination with stationary resistance electrodes of a casing containingconducting liquid compartments within th casing within one of which theelectrodes are mounted, a pump driven by the motor to be started, housedwithin a second compartment to pump liquid into the electrodecompartment to progressively immerse the electrodes to a greater extent,a flexible diaphragm across the top of the electrode compartment and acontact maker carried by the diaphragm to short circuit the electrodeswhen the pressure of the liquid in the chamber reaches predeterminedvalue.

3. An automatic rheostat :tor starting electric motors comprising thecombination with stationary resistance electrodes of a casing containingconducting liquid compartments within the casing within one of which theelectrodes are mounted, a pump driven by the motor to be started housedwithin a second compartment to pump liquid into the electrodecompartment to progressively immerse the electrodes to a greater extent,a flexible diaphragm across the top of the electrode compartment, acontact maker carried by the diaphragm to short circuit the electrodeswhen the pressure of the liquid in the chamher reaches a predeterminedvalue, means for allowing excess of liquid to return to the lowercompartment and means to prevent the liquid level from rising tooquickly.

4. An automatic rheostat for starting electric motors comprising thecombination with stationary resistance electrodes of a casing containingconducting liquid compartments within the casing within one of which theelectrodes are mounted a pump driven by the motor to be started housedwithin a second compartment to pump liquid into the electrodecompartment to progressively immerse the electrodes to a greater extent,a flexible diaphragm across the top of the electrode compartment, acontact maker carried by the diaphragm to short circuit the electrodeswhen the pressure of the liquid in the chamber reaches a predeterminedvalue, means for allowing excess of liquid to return to the lowercompartment and a plug to control the outlet volume from the pump.

5. An automatic rheostat for starting electric motors, comprising thecombination with stable resistance electrodes of a receptacle containinga liquid, compartments on each side or": this receptacle in each ofwhich the electrodes are mounted, means actuated by the motor to bestarted contained in a second compartment for releasing the fluid in thecompartment of the electrode, so as to progressively immerse theelectrodes and means for finally short circuiting them, and an auxiliaryreservoir for making up any loss of liquid.

6. An automatic rheostat for starting electric motors comprising thecombination with stationary resistance electrodes of a fluid containingcasing, compartments within the easing within one of which theelectrodes are mounted, means driven by the motor to be started, housedwithin a second compartment to lift the fluid into the electrodecompartment to progressively immerse the electrodes to a greater extent,an auxiliary reservoir for making up any loss or liquid, means forautomatically allowing the making up liquid to flow into the lowercompartment, and means for finally short circuiting the resistanceelectrodes.

7. An automatic rheostat for starting electro-motors as in claim 6having, a valve on the outlet from the reservoir, and a tube connectedthereto extending to the normal level of the liquid in the lowercompartment.

In witness whereof I afiix my signature.

RENE BENJAMIN PLANOHE.

